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Suppression of Gamow-Teller and M1 transitions in deformed mirror nuclei 25Mg and 25Al

Direct observation of K selection rules
  • Y. Shimbara
  • Y. Fujita
  • T. Adachi
  • G. P. A. Berg
  • H. Fujita
  • K. Fujita
  • I. Hamamoto
  • K. Hatanaka
  • J. Kamiya
  • K. Nakanishi
  • Y. Sakemi
  • Y. Shimizu
  • M. Uchida
  • T. Wakasa
  • M. Yosoi
Article

Abstract.

The mirror nuclei 25Mg and 25Al are expected to have very similar structures. The Gamow-Teller (GT) transitions from the \(J^{\pi} = 5/2^{ + }\) ground state of 25Mg to the excited states in 25Al were studied by high-resolution measurements of the 25Mg(\(^3{\rm He},t\)) charge-exchange reaction at \(0^{\circ}\) and at 140 MeV/nucleon. Assuming the usual \(\Delta J^{\pi} = 1^{ + }\) selection rule for the spin-isospin-type GT transitions, the states with \(J^{\pi} = 3/2^{ + }, 5/2^{ + }\), and 7/2 + should be excited. However, of the more than ten states with these \(J^{\pi}\) values below 6 MeV excitation energy, only the 5/2 + ground state and the 7/2 + , 1.613 MeV state in 25Al were strongly populated, while all other states were strongly suppressed. The analysis of M1 transitions in 25Mg also suggested a very similar feature for the analogous M1 transitions. Both 25Mg and 25Al are known to be largely deformed, and most low-lying states can be interpreted in terms of one-particle quantum numbers in the deformed potential and the associated rotational spectra. The observed suppression can be explained in terms of the K quantum number selection rules that are inherent to axially deformed nuclei.-1

Keywords

Excited State Excitation Energy Quantum Number Selection Rule Usual Selection 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin/Heidelberg 2004

Authors and Affiliations

  • Y. Shimbara
    • 1
  • Y. Fujita
    • 1
  • T. Adachi
    • 1
  • G. P. A. Berg
    • 2
    • 3
  • H. Fujita
    • 1
  • K. Fujita
    • 2
  • I. Hamamoto
    • 4
  • K. Hatanaka
    • 2
  • J. Kamiya
    • 2
  • K. Nakanishi
    • 2
  • Y. Sakemi
    • 2
  • Y. Shimizu
    • 2
  • M. Uchida
    • 5
  • T. Wakasa
    • 2
  • M. Yosoi
    • 5
  1. 1.Department of PhysicsOsaka UniversityOsakaJapan
  2. 2.Research Center for Nuclear PhysicsOsaka UniversityOsakaJapan
  3. 3.Kernfysisch Versneller InstituutAA GroningenThe Netherlands
  4. 4.Division of Mathematical Physics, LTHUniversity of LundLundSweden
  5. 5.Department of PhysicsKyoto UniversityKyotoJapan

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